(YouTube Link)
A fellow who calls himself "The Duckman" built an electrically-powered automatic crossbow. His objective was to have a usable crossbow now that arthritis prevents him from cocking each arrow, as he would on a conventional bow. The Duckman built the weapon with a magazine of 15 arrows and the battery allows him to fire 100 before replacement. I don't see his trigger finger move while he's firing, so it appears to be fully auto, rather than semi. More pictures and specifications at the link.
Link via Gizmodo
So what's next- an automatic bludgeon? Or an electric stone-thrower...?
oh, and he had very bad teeth.
I guess technically it is full auto, but it'd be pretty easy to just let go of the trigger in between shots to only get one off at a time. Plus it looks like you have to hold down the trigger to reload/cock it too.
This is just such a brilliant engineer that completely has forgotten to first and foremost apply the KISS!!!-principle (Keep It Simple Stupid!!!) on his improvement.
Over engineered? well no, he built the thing because arthritis prevents him from cocking each arrow.
And yes DUCKS!